FOSTER CITY _ Two crashes on the San Mateo Bridge -- one in the westbound direction and the other in eastbound lanes, tied up rush-hour traffic in both directions Friday afternoon.

The westbound accident, on the flat section of the bridge, totalled three cars, according to early reports from the California Highway Patrol. The eastbound crash, on the high-rise section, involved at least five vehicles and spewed a large amount of debris into the roadway.

Ambulances and fire units from both San Mateo and Alameda counties responded to the crashes, reported shortly after 4 p.m. At least four people were reported injured in one of the collisions.

Commuters were being advised to avoid the bridge until the crashes were cleared.